<?php
/**
 * CDirectoryCacheDependency class file.
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @link http://www.yiiframework.com/
 * @copyright 2008-2013 Yii Software LLC
 * @license http://www.yiiframework.com/license/
 */

/**
 * CDirectoryCacheDependency represents a dependency based on change of a directory.
 *
 * CDirectoryCacheDependency performs dependency checking based on the
 * modification time of the files contained in the specified directory.
 * The directory being checked is specified via {@link directory}.
 *
 * By default, all files under the specified directory and subdirectories
 * will be checked. If the last modification time of any of them is changed
 * or if different number of files are contained in a directory, the dependency
 * is reported as changed. By specifying {@link recursiveLevel},
 * one can limit the checking to a certain depth of the directory.
 *
 * Note, dependency checking for a directory is expensive because it involves
 * accessing modification time of multiple files under the directory.
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @package system.caching.dependencies
 * @since 1.0
 */
class CDirectoryCacheDependency extends CCacheDependency
{
    /**
     * @var string the directory whose change is used to determine if the dependency has been changed.
     * If any of the files under the directory is changed, the dependency is considered as changed.
     */
    public $directory;
    /**
     * @var integer the depth of the subdirectories to be recursively checked.
     * If the value is less than 0, it means unlimited depth.
     * If the value is 0, it means checking the files directly under the specified directory.
     */
    public $recursiveLevel = -1;
    /**
     * @var string the regular expression matching valid file/directory names.
     * Only the matching files or directories will be checked for changes.
     * Defaults to null, meaning all files/directories will qualify.
     */
    public $namePattern;

    /**
     * Constructor.
     * @param string $directory the directory to be checked
     */
    public function __construct($directory = null)
    {
        $this->directory = $directory;
    }

    /**
     * Generates the data needed to determine if dependency has been changed.
     * This method returns the modification timestamps for files under the directory.
     * @throws CException if {@link directory} is empty
     * @return mixed the data needed to determine if dependency has been changed.
     */
    protected function generateDependentData()
    {
        if ($this->directory !== null)
            return $this->generateTimestamps($this->directory);
        else
            throw new CException(Yii::t('yii', 'CDirectoryCacheDependency.directory cannot be empty.'));
    }

    /**
     * Determines the last modification time for files under the directory.
     * This method may go recursively into subdirectories if {@link recursiveLevel} is not 0.
     * @param string $directory the directory name
     * @param integer $level level of the recursion
     * @throws CException if given directory is not valid
     * @return array list of file modification time indexed by the file path
     */
    protected function generateTimestamps($directory, $level = 0)
    {
        if (($dir = @opendir($directory)) === false)
            throw new CException(Yii::t('yii', '"{path}" is not a valid directory.',
                array('{path}' => $directory)));
        $timestamps = array();
        while (($file = readdir($dir)) !== false) {
            $path = $directory . DIRECTORY_SEPARATOR . $file;
            if ($file === '.' || $file === '..')
                continue;
            if ($this->namePattern !== null && !preg_match($this->namePattern, $file))
                continue;
            if (is_file($path)) {
                if ($this->validateFile($path))
                    $timestamps[$path] = filemtime($path);
            } else {
                if (($this->recursiveLevel < 0 || $level < $this->recursiveLevel) && $this->validateDirectory($path))
                    $timestamps = array_merge($timestamps, $this->generateTimestamps($path, $level + 1));
            }
        }
        closedir($dir);
        return $timestamps;
    }

    /**
     * Checks to see if the file should be checked for dependency.
     * This method is invoked when dependency of the whole directory is being checked.
     * By default, it always returns true, meaning the file should be checked.
     * You may override this method to check only certain files.
     * @param string $fileName the name of the file that may be checked for dependency.
     * @return boolean whether this file should be checked.
     */
    protected function validateFile($fileName)
    {
        return true;
    }

    /**
     * Checks to see if the specified subdirectory should be checked for dependency.
     * This method is invoked when dependency of the whole directory is being checked.
     * By default, it always returns true, meaning the subdirectory should be checked.
     * You may override this method to check only certain subdirectories.
     * @param string $directory the name of the subdirectory that may be checked for dependency.
     * @return boolean whether this subdirectory should be checked.
     */
    protected function validateDirectory($directory)
    {
        return true;
    }
}
